Second-order many-body perturbation study of solid hydrogen fluoride under pressure

Area of Science:

• Computational Chemistry
• Condensed Matter Physics
• Materials Science

Background:

• Understanding the behavior of hydrogen-bonded solids under pressure is crucial for materials science.
• Previous studies often relied on simplified models, limiting accuracy in predicting complex vibrational properties.

Purpose of the Study:

• To apply a linear-scaling, embedded-fragment, second-order many-body perturbation (MP2) method to investigate solid hydrogen fluoride and deuterium fluoride under high pressure.
• To accurately determine structural parameters, lattice dynamics, and vibrational spectra, and compare with experimental data and simpler theoretical models.

Main Methods:

• Employed a linear-scaling, embedded-fragment, second-order many-body perturbation (MP2) method with basis sets up to aug-cc-pVTZ.
• Calculated optimized structures, lattice parameters, molar volume, phonon dispersion, and phonon density of states (DOS) for pressures from 0 to 20 GPa.
• Utilized counterpoise correction to remove basis-set superposition errors.

Main Results:

• MP2 calculations at 0 GPa showed excellent agreement with experimental structural parameters, validating the method for higher pressures.
• MP2 accurately reproduced infrared and Raman vibrational frequencies, supporting previous analyses and explaining factor-group splitting.
• The method provided quantitative accuracy for pressure dependence in the pseudo-translational region and predicted broadening of phonon bands with increasing pressure.

Conclusions:

• The MP2 method is highly accurate for predicting the properties of solid hydrogen fluoride under pressure, significantly outperforming the Hartree-Fock method.
• The three-dimensional treatment captures essential features like pseudo-translational modes and Davydov splitting, improving upon one-dimensional models.
• MP2-calculated phonon DOS is more realistic than that from 1D models, aligning with inelastic neutron scattering spectra and providing a basis for future experimental guidance.